Phase noise and waveform damage caused by self-phase modulation (SPM) or intra-channel nonlinearity are one of the sources leading to cost of a long-haul transmission optical communication system. In a coherent optical communication system, adaptive nonlinear equalization (ANLE) of a digital coherent receiver is used to compensate for nonlinear damage of self-phase modulation (as stated in Y. Gao, ECOC2009, paper 9.4.7; Z. Pan, OFC2011, paper JThA40).
Such conventional methods of adaptive nonlinear equalization are all based on a Volterra model of a single-polarization system. That is, only nonlinear damage of a single-polarization signal itself is only taken into consideration. However, intra-channel nonlinear damage of a polarization multiplexing optical communication system contains both nonlinear damage of two single-polarization signals (x-polarization signal and y-polarization signal) and crosstalk between the two single-polarization signals caused by nonlinearity of the optical fiber. Therefore, conventional methods cannot well compensate for intra-channel nonlinear damage of a polarization multiplexing optical communication system. For example, in the reference “Z. Pan, OFC2011, paper JThA40”, conventional adaptive nonlinear equalization was used in a polarization multiplexing optical communication system, and the result showed that the performances were not desired.
It should be noted that the above introduction to the background art is given for the clear and complete description of the technical solution of the present invention and for the understanding by those skilled in the art. The above technical solutions should not be deemed as being known to those skilled in the art for having been described in the background art of the present invention.